chore(deps): Relax dependency version pins for modern Python compatibility

[sr-favrev]

Summary

This PR relaxes the strict version pins in requirements.txt to allow jugaad-data to be installed alongside modern Python packages.

Changes

• click==7.1.2 → click>=7.1.2 (compatible with click 8.x)
• appdirs==1.4.4 → appdirs>=1.4.4
• beautifulsoup4==4.9.3 → beautifulsoup4>=4.9.3
• Added lxml>=4.6.0 as explicit dependency
• Updated minimum Python version to 3.9 (Python 3.6-3.8 are EOL)

Problem

Currently, jugaad-data cannot be installed in environments with modern packages like Flask 2.x, Black, or other tools that require click>=8.0. The error looks like:

ERROR: Cannot install jugaad-data and flask because these package versions have conflicting dependencies.
The conflict is caused by:
    flask 2.3.3 depends on click>=8.1.3
    jugaad-data 0.29 depends on click==7.1.2

Solution

The code uses standard click APIs that are backward compatible:

• @click.group(), @click.command(), @click.option() decorators
• click.progressbar(), click.echo()

These APIs haven't changed between click 7.x and 8.x, so the strict version pin is unnecessary.

Testing

Tested with:

• Python 3.12
• click 8.3.1
• beautifulsoup4 4.14.3

All imports and basic functionality working:

from jugaad_data.nse import NSELive, stock_df
from jugaad_data.rbi import RBI
# All imports successful

Backward Compatibility

This change is backward compatible - users with older versions of these packages can still install jugaad-data since we use >= instead of ==.